1. Field of the Invention
A knee bolster structure is disclosed for supporting a knee of a vehicle occupant in a situation wherein the vehicle is involved in a crash. The knee bolster absorbs a maximum amount of energy from an impact of an occupant's knee at a controlled rate.
2. Description of Background Art
Hithertofore, knee bolster structures have been provided for supporting the knees of a vehicle occupant during a vehicle crash. A knee bolster is effective during a crash due to the fact that an occupant is thrown forward and the lower part of his/her body tends to be thrown with his/her knees first and the upper part of the body pulled downwardly. In view of the fact that safety belts and air bag restraining devices are utilized to protect the upper portion of an occupant's body, it is necessary to provide a structure to assist in the protection of an occupant's knees.
Conventional knee bolsters are not sufficiently effective. For example, a simple knee bolster consisting of a steel plate press-formed into a box shape tends to deform very easily during the initial contact with an occupant's knees. Thereafter, the resistance of the knee bolster to the occupant's knees tends to increase sharply as deformation progresses. When a semi-cylindrical knee bolster is used, with its cylindrical surface opposing a knee of a vehicle occupant, an impact from the knee causes a central portion of the knee bolster to depress further than the parts located on either lateral side thereof. In this situation, a sharp increase in the impact force applied to the knee occurs because further deformation of the knee bolster requires a larger amount of buckling deformation. The deformation of the knee bolster is not necessarily stable. Therefore, resistance which occurs when the knee engages the knee bolster may vary depending on various conditions regarding the way in which the knee hits the knee bolster.
A knee bolster has been proposed wherein an energy absorbing member is placed opposite to a knee of an occupant of a vehicle. The energy absorbing member is disposed on a substantially rigid load supporting member. This disclosure is designed to absorb energy in a maximum amount at a controlled rate without excessive resistance to the knee.
A problem exists with regard to conventional knee bolsters used on the passenger side of a vehicle. The conventional knee bolsters are too large and thus take up too much space from the interior of a glove box which is disposed on the passenger side. In addition, the box shape of a conventional glove box tends to deform obliquely and the resistance of the glove box to the knees tends to decrease sharply as the oblique deformation progresses.